1. The problem statement, all variables and given/known data A 50-kg parachutist descends at a steady 40 km/h. What force does air exert on the parachute? 2. Relevant equations 3. The attempt at a solution Okay, I know that F_net = ma, where F_net is the net sum of all the forces acting on the parachutist. The two forces acting on him are gravity (acting downward) and the air resistance (acting upward). These forces are in opposite directions. I know that if I denote the force caused by gravity (did I word that correctly?) by F_g, then we have F_g = 50(-9.8) = -490. Now I will have F_net = F_g + F_a, where F_a is the force of the air. I imagine that I have to use the fact that he is travelling at 40 km/h downward to figure out the his net force must be, and then solve for F_a. But, the way I see it, if he is travelling at a STEADY speed of 40 km/h, then his velocity is constant. So his acceleration is 0. But then I should get a net force of 0. This doesn't seem correct to me.